diff -u b/core/lib/Drupal/Core/Cache/ChainedFastBackendFactory.php b/core/lib/Drupal/Core/Cache/ChainedFastBackendFactory.php
--- b/core/lib/Drupal/Core/Cache/ChainedFastBackendFactory.php
+++ b/core/lib/Drupal/Core/Cache/ChainedFastBackendFactory.php
@@ -17,45 +17,48 @@
   use ContainerAwareTrait;
 
   /**
-   * The service name for the consistent backend.
+   * The service name of the consistent backend factory.
    *
    * @var string
    */
-  protected $consistentService;
+  protected $consistentServiceName;
 
   /**
-   * The service name for the fast backend.
+   * The service name of the fast backend factory.
    *
    * @var string
    */
-  protected $fastService;
+  protected $fastServiceName;
 
   /**
    * Constructs ChainedFastBackendFactory object.
    *
-   * @param \Drupal\Core\Site\Settings $settings
-   *   The settings object.
+   * @param \Drupal\Core\Site\Settings|NULL $settings
+   *   (optional) The settings object.
+   * @param string|NULL $consistent_service_name
+   *   (optional) The service name of the consistent backend factory. Defaults
+   *   to:
+   *   - $settings->get('cache')['default'] (if specified)
+   *   - 'cache.backend.database' (if the above isn't specified)
+   * @param string|NULL $fast_service_name
+   *   (optional) The service name of the fast backend factory. Defaults to:
+   *   - 'cache.backend.apcu' (if the PHP process has APCu enabled)
+   *   - NULL (if the PHP process doesn't have APCu enabled)
    */
-  public function __construct(Settings $settings) {
-    // Allow settings to specify the two backend services to use.
-    $cache_settings = $settings->get('cache');
-    if (isset($cache_settings['chained_fast_cache'])) {
-      if (!empty($cache_settings['chained_fast_cache']['consistent'])) {
-        $this->consistentService = $cache_settings['chained_fast_cache']['consistent'];
-      }
-      if (!empty($cache_settings['chained_fast_cache']['fast'])) {
-        $this->fastService = $cache_settings['chained_fast_cache']['fast'];
-      }
+  public function __construct(Settings $settings = NULL, $consistent_service_name = NULL, $fast_service_name = NULL) {
+    // Default the consistent backend to the site's default backend.
+    if (!isset($consistent_service_name)) {
+      $cache_settings = isset($settings) ? $settings->get('cache') : array();
+      $consistent_service_name = isset($cache_settings['default']) ? $cache_settings['default'] : 'cache.backend.database';
     }
 
-    // Otherwise, default to database for the consistent backend, and to the
-    // APCu (if it's available) for the fast backend.
-    if (!isset($this->consistentService)) {
-      $this->consistentService = 'cache.backend.database';
-    }
-    if (!isset($this->fastService) && function_exists('apc_fetch')) {
-      $this->fastService = 'cache.backend.apcu';
+    // Default the fast backend to APCu if it's available.
+    if (!isset($fast_service_name) && function_exists('apc_fetch')) {
+      $fast_service_name = 'cache.backend.apcu';
     }
+
+    $this->consistentServiceName = $consistent_service_name;
+    $this->fastServiceName = $fast_service_name;
   }
 
   /**
@@ -70,15 +73,15 @@
   public function get($bin) {
     // Use the chained backend only if there is a fast backend available;
     // otherwise, just return the consistent backend directly.
-    if (isset($this->fastService)) {
+    if (isset($this->fastServiceName)) {
       return new ChainedFastBackend(
-        $this->container->get($this->consistentService)->get($bin),
-        $this->container->get($this->fastService)->get($bin),
+        $this->container->get($this->consistentServiceName)->get($bin),
+        $this->container->get($this->fastServiceName)->get($bin),
         $bin
       );
     }
     else {
-      return $this->container->get($this->consistentService)->get($bin);
+      return $this->container->get($this->consistentServiceName)->get($bin);
     }
   }